unable to upload images since late December 2015

Don’t drag and drop. There should be an upload button at the top of the page OR right-click on the folder or file you are going to upload and see if the option to “upload” appears.

Yep, found that. I get the drag and drop pane with the alternative option to Select File. When I do that though, and navigate to the replacement file fomr the one I downloaded, it only offers me the option of opening the wp-admin folder, not selecting it whole. (Sorry, this is probably something really obvious, but I’m stuck.) Presumably I don’t have to select and upload every document within the folder individually?

Don’t use drag and drop.
For the upload button, click on the button and a window will open that has the permissions (do not touch!) and a BROWSE button. click this and it will open in your computer. Go find the file or folder you are going to upload and select it and press OPEN.
Go back to the window where all the files are to see it uploaded – it will tell you when it is done. You may have to refresh your browser.

It seems that perhaps your host may not allow you to upload entire folders. Hang on a minute.

Did you delete all the files yet? No problem if you did.

Ok, we’re talking at cross purposes here.
This is is what I’m doing.

From public_html, I click Upload.

This opens a new window, with the message Select the file you want to upload to “/home/takahe/public_html”. There is a drag-and-drop area, marked Drop files here to start uploading or, and a radio button marked Select File.

When I click Select File, it opens a window on my computer.
I select the WordPress folder from the desktop (where I unzipped it to), get the options Open or Cancel.
I click Open, and it opens the WordPress folder. I select the wp-admin folder, but the only options I have are Open or Cancel.
When I click Open, all it does is open that folder on my desktop. The only option I have is Cancel (or presumably to select one of the files), and I cannot click back to the browser until I click Cancel.
I have tried refreshing the browser after doing that, but it hasn’t uploaded wp-admin.

I’ve only shifted the wp-admin file to the trash. Nothing else.

Yes, it seems that perhaps your host may not allow you to upload entire folders. Did you delete all the files yet? No problem if you did.

No, just put the wp-admin folder in the trash.

If it helps, FreeParking has something or other called Installatron that apparently is what I would need to use if I did a complete reinstall myself. Or do I need to do all the replacing at the level of the individual files?

No, that may not work correctly.

You will only have to do this for the wp-admin and wp-includes folders.

Right-click on the wp-admin folder and hover “send to” and select “Compressed (zipped) folder”.
This will create a zip file of the wp-admin.
go back to cPanel and Upload.
Browse for the zip file, select it and hit Open. It will upload and tell you when i is done at the bottom right of the window.
When it is done repeat the process for the wp-includes folder.

They will both be there in “zip” form.
Right click on wp-admin.zip and select “extract”
Do the same for wp-includes.zip

After they are extracted, delete their zips.

Then proceed with uploading the single files in the list,.

Ok, turning wp-admin into a zip seems to have worked, and I’ve uploaded it. Presumably I need to delete the old files (wp-admin – already done – and wp-includes) before uploading the zipped versions?

And something a little weird – extracting the folders has created a new folder on that level called __MACOSX. Inside which are what look like duplicates of the wp-admin and wp-includes folders.

Yes. delete old. Upload zips. Extract zips (there will be new wp-admin and wp-includes folders). Delete zips. Proceed with single files.

Done. And after all that, still not working. I even tried uploading a new image. Still broken.